Casein paint composition



Patented "Apr. 11, 1939 casnm ram'r comosrrroN Herman A. Schulz, onPark, m., aasignor to United States Gypsum Company, Chicago, lll., acorporation of Illinois No Drawing.

Application. February 4, 1935, Serial No. 4,871

12 Claims. (Cl. 134-46) The present invention relates to an improvedcasein paint composition that is prepared in paste form so that it maybe used as such or diluted with water to proper spreading consistency.

Oneof .the objects of the present invention is to prepare a paint fromcasein and various solvents, stabilizers, pigments andfillers which willretain is original consistency and quality unimpaired over long periodsof time without deterioration, livering, settling or hydrolysis of thecasein. A further object of the invention is to prepare a casein pasteor solution from casein, a solvent therefor, and a stabilizing agentcomprising al- I kali salts of ainphoteric metals.'

A further object of the invention relates to the method employed fromthe compounding of a casein paste paint composition in which thesequence of. operations is particularly designedto yield the bestresults with the least expenditure of time and energy.

Stilla further object of the invention is to propare a paste paint fromcasein, water, and 'al-' kaline solvents which is resistant to changesin alkalin material employed for its solution. The

action is a sort of hydrolysis of the large casein molecule or complexand is irreversible.

One of the primary objects of the present invention is, therefore, toovercome the tendency 5 of casein paste paints to deteriorate by reasonof such hydrolysis, and this is accomplished mainly by the use, togetherwith the usual alkaline solvents,'of' a stabilizing agent which preventsthe hydrolysis and, hence, the resultant loss in vis- 1'0 cosity; It hasbeen found by the inventor that alkalisalts of amphoterlc metals, suchas sodium or potassium stannate, aluminate, antimonate or vanadate, andtheir equivalents, will serve as I stablizing agents for alkaline caseinsolutions, 15 such, for example, as result from thesolution of caseininqan aqueous solution of borax or similar alkaline salt. Y

A, further advantage of a paint made in accordance with thepresentiinvention resides in the 20 fact that it has better gelcharacteristics, better flowability and enhanced brushing properties,and

when dry is more resistant to wetting and-washconsistency resulting fromhydrolysis of the i118 such as sodium, potassium, and their equivalents.

30 Other objects of the invention will be apparent from the hereuntoappended claims and the detailed description of the precessesand-products hereinbelow. j

Paste paints madeifromcasein and its equiva- 35 lent protei'dsubstances. have'already been known for some years, and their methods ofmanufac- However, has been found that such casein paints are lackinginstability and 'keepingqualities, 40 despite the fact that variouspreservatives have been added in an effort to prevent deterioration. Itappears that the main dlfiiculty with such paints is that they tend tobecome thinner with ,age, finally becoming so liquid that the pigments45 and fillers suspended therein separate from the casein vehicle andsettle to the bottomy'of the containers. Contrary to ordinary oilpaints, however, such deteriorated. paints'cannot be brought back totheir original condition by stirring and so mixing, because of the factthat the casein vehiclethat is, the casein solution-has lost itsviscosity and hence is no longer able to retain the pigments and fillersin suspension. This loss in viscosity appears to be caused by aprogressive. hydrolysis of the casein by the action of, the

and the like.

- -In general, it may he stated that the casein paints made inaccordance with the present invention consist of a vehicle andrelatively inert mineral matter in the form of fillers and pigments. ,Bythe term "pigmen the inventor intends to cover colored as well as whitepigments and also any 'mineral products used merely as The vehicleconsists of a stabilzed solution of casein in an alkali, such as borax,to which there has been added an alkali salt of an amphoteric metal. Thepigments may be of any kind, such as zinc white, zinc sulfide pigments,

ture have 'become more or less standardized. mica-ta c.- fly 'imnOxides, cadmium fi chromium oxides, ultramarine, lead chromate, I

Even carbon and shale blacks as well as organic pigments of many types,such as 40 toners and lakes, may be employed, depending upon the colordesired in the paint. The paint is manufactured and sold in the form ofa rather heavy paste somewhat resembling in consistency the pastewhite-lead familiar to the oil-paint trade. In actual use this paste isdiluted with from one-hall. to equal parts of water, whereby a. readilyspreadable or sprayable composition results. The various-formulas givenh'erelnbelow are intended to be purely illustrative and are not to beconstrued as limitations upon the invention. I

' In addition to the casein vehicle and fillers," there are also used inthese paste paints certain organic substances, such as oils and essenutial oils. These are for the purpose of waterproofing, and they also actas preservatives, plasticizers, and mold preventatives. The oils usedmay be linseed oil, 'tung oil, Perilla oil, fish oil, and the like, oreven a deodorized mineral oil; and the essential oil may be a terpenesuch as pine oil, terpineol and similar substances. The oils, such asthe linseed oil, etc., should preferably be of a type, now procurable onthe market, that exhibits only a slight tendency toward yellowing onexposure to the air in the absence of light.

A number of difierent procedural methods may be employed in compoundingthe paint. Thus, for example, a casein solution containing thestabilizer may first be prepared. To this casein solution the variouspigments, fillers, and tinting agents may be added, following which themixture may be ground in a paint mill much in the same manner that oilpaints are ground. The purpose of the grinding is to secure as smoothand uniform a mixture as possible.

An alternative method is to prepare a solution of casein containing thestabilizer and then to mix "this solution with such of the pigments asmay exhibit a slight tendency to react with the casein (as, folinstance, lithopone or 'zinc of all of the ingredients of the paint,with the exception of the oils and essential oils. This can be done, forexample, by grinding casein, or merely mixing the'casein, with the dryfillers, pigments, and tinting agents, as well as the dry solvents andstabilizers. The uniform mixture of materials thus obtained is thengradually stirred 1 into a'predetermined amount of water, and themixture is then cooked or heated until a smooth paste results. Duringthis stage of the manufacture the oils and essential oils may be added,or

they may be emulsified with a small amount of a separately preparedcasein solution and then worked into the paste paint while it is beingheated or cooked, the agitation being continued until a smooth,homogeneous paste results. By thus operating, the grinding operation inthe paint mill may be dispensed with. V

As examples of the present invention, the following may be cited:

First method Preparation of casein soZution.--82.5 pounds of commercialcasein are mixed with about 32 gallons of water. and thoroughly stirredfor a suflicient time until a smooth mixture of thoroughly soaked caseinresults. About 5 pounds and -2 ounces of sodium stannate are dissolvedin about 5 gallons of water, while in a separate container about 15pounds of borax are likewise dissolved in about 3% gallons of hot water.The sodium stannate solution is then added to the casein mixture withconstant agitation, and as soon as all of it has been added the boraxsolution is run an alkalinity equivalent to from about pH 8.0 to aboutpH 9.0. The ratio of casein to sodium stannate in the above formula issubstantially 10016.2. The sodium stannate used has the formulaNazSnOsBI-IzO. It may replaced by stoichiometrically equivalent amountsof sodium or polatter is made by taking the casein solution and.

mixing therewith pigments such as lithopone, finely ground mica, talc,etc., and an oil such as pine oil and, if desired, a plasticizer such aslinseed oil, etc., and also, if desired, a small amount of ethylalcohol. The latter is for the purpose of somewhat lowering theconsistency ofthe mixture. The pigments, etc. are mixed with the caseinsolution gradually, and 'when all has been incorporated the mixture isground in a paint mill until uniformly smooth.

The percentage composition of the solids of the casein paint made inaccordance with the present invention is. about as follows:

Per cent Cas r r 10.0 Amphoteric metal salt 0.6 Borax or equivalent .8

1 Pigments and fillers 80. Mica or equivalent 5 0ils, q. s. to makeparts.

To this there may be added about 0 parts of water to form the paste.

As further exempletive of the modifications in the composition of thesolids of the paste casein paint may be mentioned the followingformulas:

Parts Casein .Sodium stannate 3 Bor 20 Pigments and fillers 850 Pine oil10 Parts Casein 120 Sodium stannate 10 Borax- 20 Pigments and fillers850- Pine oil 10 Among the pigments may be mentioned titanium oxide,Titanox, zinc sulfide pigments, cadmium lithopone, barium sulfate, clay,mica, talc, etc.

Second method A casein solution may be prepared as given in the fi tmethod. To this may be added the required amount of zinc pigments, andthe mixture may be heated to, say, to F. until any reaction that mighttend to occur has had time to complete itself. The mixture or suspensionthus obtained is then employed as is the casein solution of the firstmethod, taking into consideration the fact that some of.the pigment hasthus already been incorporated with the paint composition. The remainderof the fillers, pigments and tinting agents, as well as the oils oressential the quantities mentiorfed:

. I amass: 3

oils, is then mixed as in the first method. where- .after the mixture isground smoothin a paint mill.

' Third method I 5 'I'his, as already briefly mentioned, cimsists inpreparing a dry mixture of the ingredients and .stirring this into therequired amount of water and heating and stirring the mixture untilsmooth. For instance, a mixture containing the various ingredients asset forth in the above percentage formula may be used, stirring the samegradually into about 30 to 35 parts of water and heating the mixture tofrom 150 to 170 1''. with constant agitation until a smooth uniformmixture results. The oils or essential oils, or

both, in the above formula are added after the I solution of the caseinduring the heatingstages or subsequently.

Irrespective as to how the mixture is made, the

final paste paint composition is then directly particular method ofcompounding the ingredi-- ents, all as set forth in the following claim.

In the hereunto appended claims, the term "mild alkali solvent" is usedto designate those alkaline-reacting alkali metal and ammonium saltsthat do not have an hydroxyl-ion concentration equal to that of thehydroxides of the alkali metals, such as sodium or potassium hydroxide.

I claim:

1. A stable aqueous casein paste paint whose viscosity andpigment-suspending properties re- -main substantially unimpairedior along time comprising water, casein,-suflloient mild alkali solvent tosolubilize the same, and, as a stabilizing agent, an alkali salt of theamphoteric metals constituting the group consisting of aluminum,

antimony, tin and vanadium, said salt being pres- .ent in an amount notexceeding that of the solvent.-

2. A- stable aqueous caseinv paste paint whose viscosity andpigment-suspending properties remain substantially unimpaired forfa longtime, comprising in addition to its water content the to followingingredients in or about theproportions .mentioned:

i Per cent Casei 10.0 Alkali salt of anamphoteric metal from the sroupconsisting of aluminum, antimony, V

' tin and vanadium 0.0

A soluble'borate 1.0

Pi ants and fillers 80.0 a? 2.0

- "and glamour caseinpaste-paint m viscosity pigment-suspendingproperties remain substantially unimpaired for a long timeoomprisingthefollowing ingredientsinorabout Parts CaseinSodimnjstannate. 8-10 Borax so Pigments and illlersuus. -s 850 Hne oil10 ih'lheproeessofpreservingforalongtimethe I t-suspen'ding ofvfllltilltyalldllalllell properties swallows-mammal casein in a mildalkali solvent which comprises adding thereto an amount of an alkalisalt of an amphoteric metal from the group consisting of aluminum,antimony, tin and vanadium not exceeding that of the said solvent. 5

5. A stable casein paste paint whose viscosity and pigment-suspendingproperties remain substantially unimpaired for a long time comprising apigment, water, casein, borax suflicient to dis-. solve the casein, and,as a stabilizing agent, sodi- 10 um stannate not to exceed one-half theamount of the v 6. A stable aqueous casein paste paint whose viscosityand pigment-suspending properties remain substantially unimpaired foralong time 15 comprising water, casein, suiiicient borax to solubiiizethe same and, as a stabilizing agent, an alkali salt of the amphotericmetals constituting the group consisting of aluminum, antimony, tin andvanadium. said salt being present in an 20 amount not exceeding that ofthe borax.

7. The process of preserving'for a long time the viscosity andpigment-suspending properties of an aqueous solution of casein in boraxwhich comprises adding thereto an amount of an alkali 25 salt of anamphoteric metal from the group consisting of aluminum, antimony, tinand vanadium not exceeding that of the borax.

8. The method of preparing a casein paint in the paste formcharacterized by its stability and so substantially uniform viscosityover long periods of time, which comprises dissolving casein in anaqueous solution of an alkaline-reacting alkali salt and of astabilizing agent consisting of an alkali metal salt of the amphoterichydroxides of 5 solution a pigment reactive with respect toastabiliflngagenaanalkallmetalsaltofthe amphoteric hydroxides of themetals from the group consisting of aluminum, antimony, tin andvanadium, and a pigment. 4 10. Aoaseinpaintinpasteform characterized byits stability and substantially uniform via; 9

-and,lsastabilizer,analkalimetalsaltofthegg amphoteric hydroxides of themetals from the group eomisting of aluminmm antimony, tin and 11. acasein solution suitable for the monie- .tion-ofacaseinplstel dn w p llwatenoo reactingcaseimasuilicientamountofanalkalinealkalisaittosolubiliaethesame, and.astabllisingagenaanalkalimetalsaltofthesmphoterichydroxidesoithemetalsfromthegrmm:

lzAnalkaline-reactin'gcaseinsolutionstabhlllodagainsthydrolysisbythepresenoetherein

